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Why is the width of the header and footer automatically 100%?
Jonathan GrieveTreehouse Moderator 91,243 Points
The body is the root element of a HTML document and by definition takes up the entire screen (or width of the browser).
If your element is a block level element then automatically it takes up the width of it's containing element, which could be the body, i.e. the root element. A width of 100% is the same as taking up the full width of the containing element.
I hope this answers your question. :)